The present invention concerns a protection tile for scroll flight wear protection.
For this type of centrifuge scroll, there is generally a tile protection avoiding flight wear and allowing for durable conveyance when the product to be transported is particularly abrasive.
These protection elements are usually fabricated using carbon tungsten or ceramics, with a coefficient of thermal expansion which can defer significantly from steel which is generally the element of the flight. Assembly of these elements is particularly delicate and several patents proposing solutions concerning rivets, glue or weld, have already been published.
One solution known from U.S. Pat. No. 4,328,925 shows the assembly via a support with grooved dove tail locking system in which an abrasive resistant element is inserted on one side and constitutes a complimentary form. The position is held via glue or deformation of tab or blocking via a plate screwed onto the support. This solution does not insure ortho-radial support of element resistant to abrasion, sufficient enough for friction of product being displaced. These elements can slip and become dislodged.
The solution in European Patent No. 0 081 938 shows an assembly using an abrasive resistant element fixed on the scroll flight using conical rivets. This solution is difficult and costly to implement due to the necessity of drilling the flights.
U.S. Pat. No. 5,429,581 shows an assembly using an abrasive resistant element with male form lodging via an axial slippage into a complimentary housing located on the scroll flight. Even though this solution satisfactory allows for bearing radial, ortho-radial and axial loads, using this method is also difficult and costly to implement due to the requirements of machining for lodgment on the flights. Maintaining tiles in lodging is insured via glue or plates, cone and screws. Multiplication of these maintaining parts can be costly.
In U.S. Pat. No. 6,206,818 an assembly solution is shown using a support with dove tail locking system grooves in which abrasion resistant element is placed present in complimentary form. This element is inserted via side entry slippage or, if space between male and female forms permits, frontal entry. Fixation of the abrasive resistant element is achieved by glue injection into the existing gaps of the support. A hole in the rear of the support and grooves over two parts allow for glue spreading over all empty spaces. This gluing is possible after welding the support on a conveyor flight, which avoids possible alteration of glue due to high temperature welds. Precise positioning of supports before weld is needed to insure final continuity of the wear resistant elements. This requires using special tools as per U.S. Pat. No. 6,230,960 which can cause a long and costly assembling.
DE 3435960 A1 shows a wear tile being one part where an additional ring is mounted in a circumferential opening at the tip of the screw blade. With this opening the screw blade is weakened and thus with high axial forces the tip of the screw blade may break.
JP 2012-551 A1 shows a protecting tile consisting of two parts. However the support is welded to the tip of the screw blade and the wear plate inserted into the support. The wear plate is fixed to the support by means of a cotter, which is inserted from the side. This however can only be done while manufacturing the apparatus. As soon as there are the protection tiles side by side, the cotter cannot be moved.
JP H03-130218 U shows a protection tile where the support is welded to the screw flight. It has a nut where a wear plate is inserted. This wear plate is then fixed by an elastic sealing. However such sealing ring would fall in aggressive (e.g. acid) environment.
U.S. Pat. No. 4,416,656 shows a wear tile consisting of a support and a wear resistant member which is secured with an additional rivet or shank, which is deformed to secure the connection.
DE 3140364 A1 describes a system where the wear resistant member is mounted directly to the screw flight. To keep the members in position pins are mounted at the upper end of the screw flight, which may weaken the flight. Further the wear resistant member must be designed new for each different width and diameter of the flight and thus cannot be used on other machines.